Elastic wave device, duplexer, and communication device

Abstract

A surface acoustic wave (SAW) device includes a piezoelectric substrate, an interdigital transducer (IDT) electrode located on an upper surface of the piezoelectric substrate, a cover covering the upper surface of the piezoelectric substrate from above the IDT electrode, at least one first via conductor extending through at least part of the cover from the upper surface of the piezoelectric substrate to an upper surface of the cover, at least one second via conductor located, on the piezoelectric substrate, inward from the first via conductor in a plan view, extending through at least part of the cover from the upper surface of the piezoelectric substrate to the upper surface of the cover, and having a smaller diameter than the first via conductor, and a conductive layer located on the upper surface of the cover and extending over an upper end of the second via conductor.

The invention claimed is: 
     
       1. An elastic wave device, comprising:
 a substrate comprising a piezoelectric substrate; 
 at least one excitation electrode located on an upper surface of the piezoelectric substrate; 
 a cover covering the upper surface of the piezoelectric substrate from above the at least one excitation electrode; 
 at least one first via conductor extending through at least part of the cover from the upper surface of the piezoelectric substrate to an upper surface of the cover; 
 at least one second via conductor located, on the piezoelectric substrate, inward from the at least one first via conductor in a plan view, the at least one second via conductor extending through at least part of the cover from the upper surface of the piezoelectric substrate to the upper surface of the cover, the at least one second via conductor having a smaller diameter than the at least one first via conductor; and 
 a conductive layer located on the upper surface of the cover or in the cover, the conductive layer extending over an upper end of the at least one first via conductor and an upper end of the at least one second via conductor, 
 wherein an upper surface of a portion of the conductive layer that extends over the upper end of the at least one first via conductor comprises a region lower than an upper surface of a portion of the conductive layer that extends over the upper end of at least one second via conductor. 
 
     
     
       2. The elastic wave device according to  claim 1 , wherein
 the conductive layer is on the upper surface of the cover. 
 
     
     
       3. The elastic wave device according to  claim 2 , wherein
 a shortest distance between a plurality of the second via conductors including the at least one second via is shorter than a shortest distance between a plurality of the first via conductors including the at least one first via. 
 
     
     
       4. The elastic wave device according to  claim 1 , wherein
 the cover comprises a resin layer comprising a single material, and 
 the at least one first via conductor has a side surface shaped differently from a side surface of the at least one second via conductor at a cross section of the resin layer orthogonal to the upper surface of the piezoelectric substrate. 
 
     
     
       5. The elastic wave device according to  claim 1 , wherein
 the cover comprises a resin layer comprising a single material, and 
 the at least one second via conductor has a first tapered portion having a smaller diameter toward the upper surface of the cover, and a second tapered portion having a larger diameter toward the upper surface of the cover. 
 
     
     
       6. The elastic wave device according to  claim 1 , wherein
 the at least one second via conductor comprises, as a plurality of second via conductors, a first row of two or more second via conductors arranged in a predetermined direction in a plan view, and a second row of two or more second via conductors arranged in the predetermined direction in a plan view, and the second via conductors in the first row are arranged at positions different from the second via conductors in the second row in the predetermined direction. 
 
     
     
       7. The elastic wave device according to  claim 1 , wherein
 the at least one excitation electrode comprises, as a plurality of excitation electrodes, a first interdigital transducer electrode, a second interdigital transducer electrode, and a third interdigital transducer electrode located on the piezoelectric substrate configured to form a multimode filter, 
 the first interdigital transducer electrode, the second interdigital transducer electrode, and the third interdigital transducer electrode are arranged in a propagation direction of elastic waves in the stated order, 
 the elastic wave device further comprises a first wire, a second wire, and a third wire located on the substrate and extending from the first interdigital transducer electrode, the second interdigital transducer electrode, and the third interdigital transducer electrode in the same direction intersecting with the propagation direction, 
 the at least one second via conductor comprises, as a plurality of second via conductors, a second via conductor on the first wire and a second via conductor located on the third wire, and 
 the conductive layer connects the second via conductor located on the first wire and the second via conductor located on the third wire. 
 
     
     
       8. The elastic wave device according to  claim 7 , wherein
 the first wire and the third wire are thicker than the second wire. 
 
     
     
       9. The elastic wave device according to  claim 1 , wherein
 the at least one excitation electrode comprises, as a plurality of excitation electrode, a plurality of interdigital transducer electrodes on the piezoelectric substrate configured to form a multimode first filter and a multimode second filter, 
 the at least one second via conductor comprises, as a plurality of second via conductors, at least one third via conductor located between the first filter and the second filter in a plan view and connected to the first filter among the first filter and the second filter, and at least one fourth via conductor located between the first filter and the second filter in a plan view and connected to the second filter among the first filter and the second filter, 
 the conductive layer comprises a first section facing the first filter among the first filter and the second filter and a second section facing the second filter among the first filter and the second filter, 
 the at least one third via conductor is connected to the first section among the first section and the second section, and 
 the at least one fourth via conductor is connected to the second section among the first section and the second section. 
 
     
     
       10. The elastic wave device according to  claim 1 , wherein
 the conductive layer is on the upper surface of the cover, 
 the elastic wave device further comprises an insulating layer covering the conductive layer, and 
 the insulating layer is over the at least one second via conductor without being over the at least one first via conductor. 
 
     
     
       11. A duplexer, comprising:
 a transmission filter connected to a terminal; and 
 a reception filter connected to the terminal, 
 wherein the transmission filter and/or the reception filter includes the elastic wave device according to  claim 1 . 
 
     
     
       12. A communication apparatus, comprising:
 an antenna; 
 the elastic wave device according to  claim 1  connected to the antenna; and 
 
       an integrated circuit connected to the elastic wave device.